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Difficulty: MediumNormal Pregnancy and Prenatal Care

A healthy nulliparous patient at 6 weeks gestation by last menstrual period presents to the obstetrics clinic to establish care following a positive home pregnancy test. She is 27 years old, has an unremarkable medical history, and takes only a daily prenatal vitamin. The patient is eager to understand the timeline of her upcoming evaluations. Arrange the following routine prenatal assessments and interventions in the correct chronological sequence they should be performed throughout an uncomplicated pregnancy.

  1. 1Transvaginal ultrasound for pregnancy dating and viability
  2. 2First-trimester combined screening for fetal aneuploidy
  3. 3Comprehensive fetal anatomic survey via transabdominal ultrasound
  4. 450-g, 1-hour oral glucose challenge test
  5. 5Rectovaginal culture for group B Streptococcus

Answer

The correct chronological sequence is: dating ultrasound (6-10 weeks), first-trimester aneuploidy screening (10-14 weeks), anatomic survey (18-22 weeks), oral glucose challenge test (24-28 weeks), and group B Streptococcus culture (36-38 weeks).
Routine prenatal care follows a standardized chronological timeline to optimize maternal and fetal outcomes. Early in the first trimester (6-10 weeks), a transvaginal ultrasound is typically performed to confirm viability and establish highly accurate pregnancy dating. Between 10 and 14 weeks, first-trimester combined screening (nuchal translucency and serum markers) is offered for aneuploidy risk assessment. The comprehensive fetal anatomic survey is optimally performed between 18 and 22 weeks, as fetal structures are adequately developed for visualization. Universal screening for gestational diabetes with a 50-g oral glucose challenge test is conducted between 24 and 28 weeks due to the physiological peak in insulin resistance caused by placental hormones. Finally, rectovaginal screening for Group B Streptococcus is performed between 36 and 38 weeks to maximize the predictive value for intrapartum colonization status.

Step-by-Step Solution

1
Determine the timing for the initial viability and dating scan.
First trimester, typically 6-10 weeks.
Establishing accurate gestational age and confirming viability is the foundational first step in prenatal care.
2
Identify the window for first-trimester aneuploidy screening.
10-14 weeks.
Nuchal translucency and specific maternal serum markers must be evaluated within this narrow gestational window for accurate risk calculation.
3
Identify the timing for the comprehensive anatomic survey.
18-22 weeks.
Fetal structures, including the heart and central nervous system, are best visualized transabdominally at this mid-trimester stage.
4
Determine the optimal window for universal gestational diabetes screening.
24-28 weeks.
Placental hormone production (such as human placental lactogen) peaks during this time, maximizing insulin resistance and the detection of gestational diabetes.
5
Determine the timing for group B Streptococcus (GBS) screening.
36-38 weeks.
GBS screening is conducted late in the third trimester to accurately predict intrapartum colonization status and guide the need for antibiotic prophylaxis.

Key Concept

Chronological timeline of routine prenatal care interventions in an uncomplicated pregnancy.
Estimated Time:1m 0s
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Topics

Normal Pregnancy and Prenatal Care

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